I just booked RT from Dallas for 2 for 55,000 miles on Aadvantage. The return trip is great - depart 3:25 to CLT with 2 hr layover, then arr in DFW at 10:24. The outbound is not so great, DFW at 9:00, IAH, MIA, then arr SXM at 10:24.
Last March we went from SAT at 6:05 to MIA, arr SXM 2:15, the return pretty much the same as this year, but SAT instead of DFW, for 50,000. Today it would have been 27,500 pp each way. Anything cheaper would require an overnight both ways. We have to drive to Dallas and back, but we're travelling with friends from Dallas, so no big deal. Taking out a new card every 18 months and getting 50,000 miles for charging $3000, makes it pretty cheap, even with the $150 or so fees.